1. Field
The present disclosure generally relates to electronic reference devices and, in particular, to low-power, temperature-compensated crystal oscillators.
2. Description of the Related Art
Crystal oscillators are often used as reference sources for time in electronic circuits. The frequency of the oscillatory signal generated by the crystal is affected by the temperature of the crystal. When it is desired to stabilize the oscillation frequency of the crystal to less than one part per billion per minute, or to use the oscillations to create a clock with an accuracy of one second per year, it is desirable to stabilize the temperature of the crystal oscillator. Some conventional temperature stabilization systems use a feedback-controlled heater to maintain the temperature of the crystal at a desired level, but this consumes more power than may be desirable as the target temperature of the crystal must be above the highest expected ambient temperature. The power consumption of current technology for time reference devices having a stability of 0.25 parts-per-billion per minute (ppb/min) is about approximately 350 milliwatts (mW) for oven-controlled oscillators and 125 mW for chip-scale atomic clocks.